The invention relates to apparatus for curing ink, paint and other coatings particularly on plastic, glass or metal bottles and jars or other containers as well as other articles. Ultraviolet curable inks are widely used to print product labels on products and the containers for products. While the invention has particular application to ultraviolet light curing by photopolymerization of ultraviolet light curable ink and other coatings it will be understood that some forms of the invention may be also applied to other applications. Similarly, while the invention has particular application to the curing of coatings on relatively small articles it will be understood that other forms of the invention may also be utilized on much larger articles.
The prior art includes apparatus such as the Ultraviolet Light Curing Apparatus described in U.S. Pat. No. 4,573,277 issued on Mar. 4, 1986 to Donald L. Sudduth. The apparatus described therein employs a rotating table apparatus having an entrance port area defined at one circumferential part. Guide members direct the article from the outer edge of the rotating table to the center of the table and back out to the outer part of the rotating table. The apparatus utilizes reflectors to achieve the desired cure. This mechanism with the reflectors and the mechanism for moving each article sequentially from the circumference of the rotating table to the center of the rotating table and then to the circumference of the rotating table is undesirably complex.
More particularly, the apparatus of Sudduth utilizes a rotary construction in which a plurality of workstations are disposed about the peripheral edge of a rotary table. As the rotary table moves about a vertical axis, each workstation passes sequentially to a loading position, a radiation position and an unloading position. The apparatus described therein suffers from substantial losses of ultraviolet energy. More specifically, these losses are caused by (1) energy from the ultraviolet light source not being focused, (2) the use of one or more reflectors and (3) by the use of mirrors. For example, the energy loss from a mirror is approximately 30 percent of the energy that is incident on that mirror. It is desirable to avoid such losses since they are prejudicial to achieving a uniform high quality cure.
It is an object of the present invention to provide apparatus having a relatively simple construction.
Another object of the invention is to provide apparatus that does not rely on the use of reflectors to achieve a proper cure of the coating on the work piece.
Still another object of the invention is to provide apparatus that has safety provisions to minimize the risk of injury to the operator of the apparatus.
Yet another object of the invention is to provide apparatus that will function with a wide variety of different work piece shapes, including rotationally symmetrical objects, oval objects and relatively flat objects, without the use of shutters or sensors for exposure control.
An additional object of the invention is to provide apparatus that facilitates rapid placement of work pieces within the apparatus and rapid removal of work pieces from the apparatus.
It has now been found that these and other objects of the invention may be attained in an apparatus for curing ink, paint and coatings on containers and articles which includes a rotatably mounted assembly that includes, in a preferred form, a plurality of workstations disposed about the periphery thereof and an emitter disposed next to the periphery of the rotatably mounted assembly and apparatus that sequentially positions respective workstations directly in front of the emitter.
In some forms of the invention the emitter is an ultraviolet radiation emitter and the apparatus for sequentially positioning includes apparatus for causing the workstations to dwell next to the emitter. The apparatus may further include apparatus for selectively rotating at least some of the workstations when a respective workstation is disposed next to the emitter and apparatus for holding an associated work piece on the workstations. Some forms of the apparatus for sequentially positioning include a mechanical mechanism which may be a Geneva mechanism. The apparatus for rotating each of the workstations may include a roller which may cooperate with a motor. Other forms of the invention include apparatus for changing the position at which any dwell occurs during the rotational cycle of the rotatably mounted assembly. Other forms of the invention includes apparatus for causing the dwell to occur simultaneously with at least two workstations being equally distant from the emitter.